On one hand he clearly states that "The agreement requires matching Steam functionality" which is good news, as it clearly proves that GOG is doing what so many customers demanded: to force devs to give to GOG userbase the same benefits that steam users have.
What irks me is that this should be a standard, and not GOG trying to "force" devs to respect this.
My only fear is wether GOG has been losing some games, these last years, just because the devs refused to create achievements for Galaxy and GOG thus refused to sell their games. But maybe I'm just reading too much into it.
Let them be. If achievements have become a standard for the gaming industry and they still refuse to put them on GOG due to lazyness/not wanting to be arsed with for a GOG release, then I have no doubts that this could extends in the future as delayed updates, new content, and so on.
I never cared for achievements in the first place, but there is a big difference between truly struggling to implement them, or not wanting to do that out of lazyness.
I must say that I'm glad that GOG requires matching Steam functionality and that they include achievements.
There are several advantages that I would like to point out:
1. GOG users have always been asking for full games in every component, and releasing games without them always generates discontent. Just think that if the multiplayer is missing compared to Steam, the game is always harshly criticized. It's a first step to have fewer games that end up in the 2nd class list.
2. Achievements sell, some people do not buy on GOG for their lack, and GOG has extreme need to attract new paying users and not only the usual leeches who want the game for free with GOG Connect.
3. This clause eliminates developers who use GOG only for some easy money and then disappear forever and abandon the game. Personally I prefer less games but complete. If someone decides not to release a game on GOG for this reason, he wasn't a reliable developer.
4. As you can see from the thread, this can finally lead to a more widespread diffusion and understanding of the GOG SDK, which will consequently make everything easier as it's for Steam.
5. Evidently it's not even a really mandatory requirement, because unfortunately many developers still release games without achievements (very recent example P.A.M.E.L.A.).
SO MUCH THIS! It's not about getting achievements or not, but overall parity, which not only will make GOG look like a more reliable platform, but also making it more popular, while lessening those botched release only GOG gets (be them delayed/stopped updates, DLC, or altogether cut features).